Several publications and patent documents are cited throughout the specification in order to describe the state of the art to which this invention pertains. Each of these citations is incorporated herein by reference as though set forth in full.
The precise targeting specificity of antibody molecules makes them attractive vehicles for tumor imaging and therapy agents. Employing an antibody with a high affinity for an antigen that is uniquely or predominantly expressed on cancer cells can lead to a greater specificity of tumor retention, thereby increasing the likelihood of successful treatment or detection. While the initial clinical trials of antibody-based tumor targeting revealed a number of hurdles (e.g., the immunogenicity of the murine monoclonal antibodies, the poor tumor penetration of immunoconjugates and a lack of tumor specificity of the antigenic targets), these have largely been addressed over the past decade. Anti-tumor antibodies are now developed using human immunoglobulin genes, resulting in proteins that are rarely seen as foreign. The degree of tumor penetration and the rate of systemic elimination of toxic immunoconjugates have been improved through the development of novel, minimal antibody-based structures (e.g., monovalent and divalent single-chain Fv [scFv] molecules). In preclinical models, this has simultaneously increased the fraction of the tumor that is treated and reduced the exposure of normal tissues (e.g., bone marrow) to the immunoconjugate (Adams, G. P. (1998) In Vivo, 12:11-22). Additionally, a second generation of tumor-associated or tumor-specific antigenic targets combines a predominantly tumor-specific expression pattern with an antibody-triggered alteration in intracellular signaling. The targeting of cytotoxic agents, such as radioisotopes or drugs, to such an antigen can lead to an additive or synergistic anti-tumor effect.
Monoclonal antibody (MAb)-based immunotherapy has shown notable promise in the treatment of hematologic malignancies (Kaminski, M. S., et al. (1993) N. Engl. J. Med., 329:459-465; Press, O. W., et al. (1993) N. Engl. J. Med., 329:1219-1224). Despite some constraints imposed by tumor physiology (Jain, R. K., et al. (1987) 47:3039-3051), two of the four members of the HER/EGF receptor family have proven to be useful targets for antibody-based therapy of cancer. MAbs specific for HER2/neu (Harweth, I. M., et al. (1993) Br. J. Cancer, 68:1140-1145) and EGFR (Fan, Z., et al. (1993) 53:4322-4328) can inhibit the growth of human tumors that overexpress their respective target antigens in immunodeficient mice. Treatment with a humanized form of the anti-HER2/neu 4D5 MAb (HERCEPTIN™) leads to clinical responses alone and in combination with chemotherapy agents in clinical trials and is licensed for use in breast cancer (Baselga, J., et al. (1996) J. Clin. Oncol., 14:737-744; Baselga, J. (2001) J. of Cancer, 37Suppl:S18-24). A number of clinical trials also have focused on the efficacy of antibodies that target therapeutic radioisotopes to tumors (radioimmunotherapy or RAIT). Of note, the U.S. Food and Drug Administration (F.D.A.) has approved commercial RAIT drugs ZEVALIN™, a conjugate of an anti-CD20 monoclonal antibody and the beta-emitting radioisotope Yttrium-90 [90Y] for the treatment of non-Hodgkin's lymphoma, and BEXXAR®, iodine-131 [13I] Tositumomab for the treatment of non-Hodgkin's lymphoma.
Radiolabeled MAbs have also been used for the radioimmunodetection (RAID) of a number of types of tumors including pancreatic cancer (Gold, D., et al. (2001) Crit. Rev. Oncol.-Hemat., 39:147-154), non small cell lung cancer (Schillaci, O., et al. (2001) Anticancer Res., 221:3571-3574), ovarian cancer (Kalofonos, H. P., et al. (1999) Acta Oncol., 38:629-634), colorectal carcinoma (Wong, J., et al. (1997) J. of Nuc. Med., 38:1951-1959; Willkomm, P., et al. (2000) J. of Nuc. Med., 41:1657-1663), and prostate cancer (Fang, D. X., et al. (2000) Tech. Urology, 6:146-150). These studies report the ability to detect lesions that are detectable by other methodologies (e.g., computerized tomography (CT) and magnetic resonance imaging; MRI). Immunodetection can be improved upon, however, by employing smaller, engineered antibody-based molecules such as scFv (Begent, R. H., et al. (1996) Nat. Med., 2:979-984). When isotopes with relatively short half-lives are to be used, molecules like the small, divalent diabody should exhibit the greatest degree of specific tumor localization in a setting of low normal organ background (Williams, L. E., et al. (2001) Cancer Biother. And Radiopharm., 16:25-35). Furthermore, RAID studies can be effectively utilized to acquire predictive dosimetry for use in planning or ensuring safety of subsequent RAIT studies.
Mullerian inhibiting substance (MIS) is a member of the transforming growth factor-β (TGFβ) superfamily of secreted protein hormones that signal through receptor complexes of type I and type II serine/threonine kinase receptors. The binding of MIS ligand to its receptor initiates a signaling cascade, including phosphorylation of Smad1, that is dependent on recruitment of type I receptors, ALK2 and ALK6, which also signal for bone morphogenetic proteins (Segev, D. L., et al. (2001) J. of Biol. Chem., 276:26799-26806). In males, MIS is produced in fetal and postnatal testes. MIS binds to its receptor and triggers regression of the Mullerian ducts, the anlagen of the uterus, fallopian tubes and vagina (Hudson, P. L., et al. (1990) J. Clin. Endocrinol. Metab., 70:16-22). In contrast, MIS is not produced in females until adolescence, thus allowing the above tissues to develop (Hudson, P. L., et al. (1990) J. Clin. Endocrinol. Metab., 70:16-22).
In adult females, MIS type II receptor (MISIIR) is expressed on the surface epithelium of the ovaries (Masiakos, P. T., et al. (1999) Clin. Cancer Res., 5:3488-3499). In mice, MISIIR mRNA has been detected in ovarian surface epithelium (MOSE cells) and ovarian tissue (Connolly, D. C., et al. (2003) Cancer Res., 1389-1397). In rats, MISIIR mRNA has been detected in embryonic, pubertal, and adult testes; the uterus; the ovaries; and the embryonic lung (Teixeira et al. (1996) Endocrinology, 137:160-165; Catlin et al. (1997) Endocrinology, 138:790-796). Additionally, MISIIR has been detected in human cervical cancer cells, prostate cancer cells, breast epithelial cells, breast cancer cell lines, breast fibroadenomas, breast tumors, and ductal carcinomas (Segev et al. (2000) J. Biol. Chem., 275:28371-28379; Segev et al. (2001) J. Biol. Chem., 276:26799-26806; Segev et al. (2002) Proc. Natl. Acad. Sci., 99:239-244; Barbie et al. (2003) Proc. Natl. Acad. Sci., 100:15601-15606).
Coelomic epithelium is the most common origin of human ovarian cancers and tumors of this origin express the MIS type II receptor. MISIIR mRNA is expressed in a number of ovarian carcinoma cell lines, including OVCAR3, OVCAR5, OVCAR8, OV1063 and SKOV3 (Masiakos, P. T. et al., (1999) Clin. Cancer Res., 5:3488-3499). Furthermore, recombinant MIS bound tumor cells isolated from ascites in 15 of 27 (56%) ovarian cancer patients and the binding of recombinant MIS to these tumor cells led to significant growth inhibition in 22/27 (82%) of these cases (Masiakos, P. T. et al., (1999) Clin. Cancer Res., 5:3488-3499). These findings demonstrate the relevance of MISIIR for anti-cancer therapies, particularly ovarian cancer.